/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/sched/sched_addreadytorun.c
 *
 *   Copyright (C) 2007-2009, 2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <stdbool.h>
#include <queue.h>
#include <assert.h>

#include "sched/sched.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name:  sched_addreadytorun
 *
 * Description:
 *   This function adds a TCB to the ready to run
 *   list.  If the currently active task has preemption disabled
 *   and the new TCB would cause this task to be pre-empted, the
 *   new task is added to the g_pendingtasks list instead.  The
 *   pending tasks will be made ready-to-run when preemption
 *   is unlocked.
 *
 * Inputs:
 *   btcb - Points to the blocked TCB that is ready-to-run
 *
 * Return Value:
 *   true if the currently active task (the head of the ready-to-run list)
 *   has changed.
 *
 * Assumptions:
 * - The caller has established a critical section before
 *   calling this function (calling sched_lock() first is NOT
 *   a good idea -- use irqsave()).
 * - The caller has already removed the input rtcb from
 *   whatever list it was in.
 * - The caller handles the condition that occurs if the
 *   the head of the ready-to-run list is changed.
 *
 ****************************************************************************/

bool sched_addreadytorun(FAR struct tcb_s *btcb)
{
	FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head;
	bool ret;

	/* Check if pre-emption is disabled for the current running task and if
	 * the new ready-to-run task would cause the current running task to be
	 * pre-empted.
	 */

	if (rtcb->lockcount && rtcb->sched_priority < btcb->sched_priority) {
		/* Yes.  Preemption would occur!  Add the new ready-to-run task to the
		 * g_pendingtasks task list for now.
		 */

		sched_addprioritized(btcb, (FAR dq_queue_t *)&g_pendingtasks);
		btcb->task_state = TSTATE_TASK_PENDING;
		ret = false;
	}

	/* Otherwise, add the new task to the ready-to-run task list */

	else if (sched_addprioritized(btcb, (FAR dq_queue_t *)&g_readytorun)) {
		/* Inform the instrumentation logic that we are switching tasks */

		sched_note_switch(rtcb, btcb);

		/* The new btcb was added at the head of the ready-to-run list.  It
		 * is now to new active task!
		 */

		ASSERT(!rtcb->lockcount && btcb->flink != NULL);

		btcb->task_state = TSTATE_TASK_RUNNING;
		btcb->flink->task_state = TSTATE_TASK_READYTORUN;
		ret = true;
	} else {
		/* The new btcb was added in the middle of the ready-to-run list */

		btcb->task_state = TSTATE_TASK_READYTORUN;
		ret = false;
	}

	return ret;
}
